TW202242911A - electrode - Google Patents

Abstract

This electrode (1) comprises a base material (2) and a conductive carbon layer (3) in sequence toward one side in the thickness direction. The conductive carbon layer (3) contains less than 10% by atom of gold nanoparticles that are dispersed in the conductive carbon layer (3). The conductive carbon layer (3) contains atoms to be sp3-bonded and atoms to be sp2-bonded. The ratio of the atoms to be sp3-bonded to the sum of the atoms to be sp3-bonded and the atoms to be sp2-bonded ((sp3)/(sp3 + sp2)) is 0.25 or more.

Description

electrode

The present invention relates to an electrode.

An electrode having a conductive carbon layer in which gold nanoparticles are dispersed is known (see Patent Document 1 below). Patent Document 1 discloses that the content of gold nanoparticles in the conductive carbon layer is 10 atomic % to 22 atomic %. Also, in Example 2 of Patent Document 1, the content of gold nanoparticles is 17 at%. Also, in the conductive carbon layer of Example 2, the ratio (sp ³ /(sp ³ +sp ² )) of sp ³ bonded atoms to the total of sp ³ bonded atoms and sp ² bonded atoms was as low as 0.20 . [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2016-065815

[Problem to be solved by the invention]

In the case where the ratio of sp ³ bonded atoms (sp ³ /(sp ³ +sp ² )) is relatively low at 0.20, as disclosed in Patent Document 1, as long as the content of gold nanoparticles is 10 atomic % Above, you can get stronger signal strength.

On the other hand, if the concentration of the measurement object of the electrode is low, a low signal strength can be obtained, so a high signal-to-noise ratio (S/N ratio) is required.

However, in the electrode described in Patent Document 1, there is an abnormality in which the above-mentioned high signal-to-noise ratio cannot be obtained.

The invention provides an electrode with a higher signal-to-noise ratio. [Technical means to solve the problem]

Therefore, the inventors of the present invention found that as long as the ratio of sp ³ bonded atoms (sp ³ /(sp ³ +sp ² )) is a high ratio of 0.25 or more, it is surprising that by making gold nanoparticles contain When the ratio is as low as less than 10 atomic %, a higher signal-to-noise ratio can be obtained, thus completing the present invention.

The present invention (1) includes an electrode comprising a base material and a conductive carbon layer sequentially facing one side in the thickness direction, and the conductive carbon layer contains gold dispersed in the conductive carbon layer of less than 10 atomic %. In the nanoparticle, the above-mentioned conductive carbon layer includes sp ³ bonded atoms and sp ² bonded atoms, and the ratio of sp ³ bonded atoms to the total of sp ³ bonded atoms and sp ² bonded atoms (sp ³ /( sp ³ +sp ² )) is 0.25 or more.

The present invention (2) includes the electrode described in (1), wherein the content ratio of the gold nanoparticles in the conductive carbon layer is less than 5 atomic %. [Effect of Invention]

The electrode of the present invention can obtain a higher signal-to-noise ratio.

<An embodiment> One embodiment of the electrode of the present invention will be described with reference to FIG. 1 .

<Electrode 1> As shown in FIG. 1 , the electrode 1 extends in a plane direction perpendicular to the thickness direction. The electrode 1 has one surface in the thickness direction, and the other surface separated from the one surface in the thickness direction.

The electrode 1 includes a base material 2 and a conductive carbon layer 3 arranged on one surface of the base material 2 in the thickness direction. That is, the electrode 1 includes the base material 2 and the conductive carbon layer 3 in this order toward one side in the thickness direction. Preferably, the electrode 1 only includes the base material 2 and the conductive carbon layer 3 .

<Substrate 2> The substrate 2 forms the other surface of the electrode 1 in the thickness direction. As the base material 2, an inorganic base material and an organic base material are mentioned, for example. As an inorganic base material, silicon and glass are mentioned, for example. As an organic base material, polyethylene terephthalate is mentioned, for example. As the material of the base material 2, other known materials can also be preferably used. From the viewpoint of electrode activity, an inorganic substrate is preferable, and silicon is more preferable. When the material of the base material 2 is silicon, for example, a silicon wafer is prepared as the base material 2 .

The thickness of the substrate 2 is not limited. The thickness of the substrate 2 is, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more; and, for example, 1000 μm or less, preferably 500 μm or less, more preferably 100 μm or less.

＜Conductive carbon layer 3＞ The conductive carbon layer 3 forms one surface of the electrode 1 in the thickness direction. The conductive carbon layer 3 has conductivity. The conductive carbon layer 3 is in contact with one surface of the substrate 2 in the thickness direction.

The conductive carbon layer 3 contains a plurality of gold nanoparticles 5 . A plurality of gold nanoparticles 5 are dispersed in the conductive carbon layer 3 . Specifically, the conductive carbon layer 3 includes, for example, a carbon matrix 4 and a plurality of gold nanoparticles 5 .

The carbon matrix 4 is the main part of the conductive carbon layer 3 .

The carbon matrix 4 contains carbons with sp ² bonds and carbons with sp ³ bonds. That is, the carbon matrix 4 is a microcrystalline domain having a graphite structure and a diamond structure. Thereby, the conductive carbon layer 3 has good conductivity, chemically stable structure and low background noise. As a result, the sensitivity to the measurement object is sufficiently improved.

In the conductive carbon layer 3 , the ratio of the number of sp ³ bonded atoms to the sum of the number of sp ³ bonded atoms and the number of sp ² bonded atoms (sp ³ /(sp ³ +sp ² )) is 0.25 or more.

In the conductive carbon layer 3, as long as the ratio of the number of sp ³ bonded atoms to the sum of the number of sp ³ bonded atoms and the number of sp ² bonded atoms (sp ³ /(sp ³ +sp ² )) does not reach 0.25, the The noise ratio becomes lower.

In the conductive carbon layer 3, the ratio of the number of sp ³ bonded atoms to the sum of the number of sp ³ bonded atoms and the number of sp ² bonded atoms (sp ³ /(sp ³ +sp ² )) is preferably 0.30 or more, more preferably It is preferably at least 0.35, and more preferably at least 0.40.

In the conductive carbon layer 3, the ratio of the number of sp ³ bonded atoms to the sum of the number of sp ³ bonded atoms and the number of sp ² bonded atoms (sp ³ /(sp ³ +sp ² )) is preferably 0.95 or less, more preferably Preferably it is 0.90 or less, more preferably 0.75 or less, especially preferably 0.60 or less. As long as the ratio (sp ³ /(sp ³ +sp ² )) of the number of sp ³ bonding atoms is not more than the above-mentioned upper limit, excellent conductivity in the conductive carbon layer 3 can be ensured.

The method of measuring the ratio (sp ³ /(sp ³ + sp ² )) of the number of sp ³ bonded atoms is described in Examples described later.

Furthermore, a small amount of unavoidable impurities are allowed to be mixed into the carbon matrix 4 . As unavoidable impurities, oxygen, argon, and nitrogen are mentioned, for example.

Gold nanoparticles 5 are uniformly dispersed in the carbon matrix 4 . The median diameter of the gold nanoparticles 5 is, for example, greater than 0.1 nm, preferably greater than 1 nm; and, for example, less than 20 nm, preferably less than 10 nm.

Parts of the plurality of gold nanoparticles 5 are exposed from one surface in the thickness direction of the carbon matrix 4 . In the present embodiment, in the conductive carbon layer 3 , the exposed front end (one end edge) of the gold nanoparticles 5 is located on the outermost side in the thickness direction.

The content rate of the gold nanoparticles 5 in the conductive carbon layer 3 is less than 10 atomic %.

In the conductive carbon layer 3, when the ratio of the number of sp ³ bonding atoms (sp ³ /(sp ³ + sp ² )) is 0.25 or more, the chennai in the conductive carbon layer 3 If the content rate of the rice particle 5 is 10 atomic % or more, the signal-to-noise ratio will become low.

The content ratio of the gold nanoparticles 5 in the conductive carbon layer 3 is preferably 9 atomic % or less, more preferably 7 atomic % or less, more preferably 6 atomic % or less, especially preferably 5 atomic % or less; furthermore It is more suitably less than 5 atomic %, more suitably 4 atomic % or less, and still more suitably 3 atomic % or less.

The lower limit of the content ratio of the gold nanoparticles 5 in the conductive carbon layer 3 is not limited. The content ratio of the gold nanoparticles 5 in the conductive carbon layer 3 is, for example, more than 0 at%, preferably at least 0.1 at%, more preferably at least 0.5 at%, still more preferably at least 1 at%, and especially preferably at least 0.1 at%. 2 atomic % or more.

The content ratio of the gold nanoparticles 5 in the conductive carbon layer 3 is described in Examples described later.

The thickness of the conductive carbon layer 3 is, for example, not less than 0.1 nm, preferably not less than 0.2 nm; and not more than 100 nm, preferably not more than 50 nm.

The surface resistance Rs of one surface in the thickness direction of the conductive carbon layer 3 is, for example, 1.0×10 ⁴ Ω/□ or less, preferably 1.0×10 ³ Ω/□ or less.

The thickness of the electrode 1 is the total thickness of the substrate 2 and the conductive carbon layer 3, specifically, for example, more than 0.1 μm, preferably more than 0.5 μm, more preferably more than 1 μm; and, for example, less than 1000 μm, Preferably it is 500 μm or less, more preferably 100 μm or less.

<Manufacturing method of electrode 1> Next, a method of manufacturing the electrode 1 will be described.

First, in this method, a substrate 2 is prepared.

Next, a conductive carbon layer 3 is formed on one side of the substrate 2 in the thickness direction. As a formation method of the electroconductive carbon layer 3, a dry method is mentioned, for example. As a dry method, a PVD method (physical vapor deposition method) and a CVD method (chemical vapor deposition method) are mentioned, for example. As a dry method, a PVD method is preferable, for example. As the PVD method, for example, sputtering, vacuum deposition, laser deposition, and ion plating (arc deposition) may be mentioned. Preferably, sputtering is mentioned.

As sputtering, for example, unbalanced magnetron sputtering (UBM sputtering), high-power pulse sputtering, electron cyclotron resonance sputtering, RF (Radio Frequency, radio frequency) sputtering, DC (Direct Current, direct current) Sputtering (DC magnetron sputtering), DC pulse sputtering, and ion beam sputtering. More preferably, UBM sputtering may be mentioned.

As a target at the time of sputtering, sintered carbon and gold are mentioned, for example. A target is provided in a sputtering apparatus. Two targets were installed in the sputtering apparatus. Moreover, a sputtering apparatus is equipped with a film formation means, for example. As a film-forming member, a film-forming plate (film-forming substrate) and a film-forming roll are mentioned, for example. The film forming member and the target system are arranged facing each other at a distance from each other. The target and the film forming member can apply required electric power and voltage respectively. The power and voltage are appropriately set according to the content ratio of gold nanoparticles 5 and the ratio of sp ³ in the conductive carbon layer 3 . Furthermore, since the voltage applied to the film-forming member has the effect of accelerating the speed of sputtering gas ions colliding with the film-forming member, it is called an ion accelerating voltage.

As a sputtering gas introduced into a sputtering apparatus, an inert gas is mentioned, for example. The inert gas includes, for example, argon. The pressure at the time of performing sputtering is 1 Pa or less, for example.

Thereby, the electrode 1 provided with the base material 2 and the conductive carbon layer 3 sequentially on one side in the thickness direction was obtained.

<Application of Electrode 1> Electrode 1 can be used as various electrodes, preferably can be used as the electrode that can be used as the electrochemical determination of implementing electrochemical determination method, specifically can be used as the working electrode (working electrode) of implementing cyclic voltammetry (CV); Implement The active electrode (working electrode) of square wave voltammetry (SWV), anodic precipitation voltammetry (ASV), and amperometric method.

In particular, the electrode 1 is preferably used as a chemical compound classified in groups 14 to 15 in the periodic table specified by IUPAC (International Union of Pure and Applied Chemistry) in 2019. An electrode with a high signal-to-noise ratio (working electrode) for metal elements in the group. The electrode 1 is preferably preferably used as an electrode (working electrode) with a high signal-to-noise ratio for the metal elements of the 15th group, and is more preferably used as an electrode (working electrode) that is more suitable for arsenic (specifically, trivalent arsenic ions) ) The electrode with a high signal-to-noise ratio (working electrode).

<Effect of One Embodiment> In this electrode 1, since the conductive carbon layer 3 contains gold nanoparticles 5 of less than 10 atomic %, the ratio of sp ³ bonded atoms (sp ³ /(sp ³ +sp ² )) is 0.25 or more, so the signal-to-noise ratio is high.

In particular, a high signal-to-noise ratio can be obtained as long as the electrode 1 is used as an electrode for the determination of metal elements classified in Groups 14 to 15, specifically arsenic.

＜Changed example＞ In the modified example, the same reference numerals are assigned to the same components and steps as those in the first embodiment, and detailed description thereof will be omitted. In addition, unless otherwise specified, the modified example can have the same operation and effect as that of the first embodiment. Furthermore, one embodiment and its modifications can be combined as appropriate.

As shown in FIG. 1 , in one embodiment, an electrode 1 includes a substrate 2 and a conductive carbon layer 3 . On the other hand, although not shown, the modified example includes one layer of base material 2 and a plurality of layers (specifically, two layers) of conductive carbon layer 3 . That is, the electrode 1 may include a plurality of layers (specifically, two layers) of conductive carbon layers 3 with respect to one layer of the base material 2 . When the electrode 1 has two conductive carbon layers 3, the conductive carbon layer 3, the base material 2, and the conductive carbon layer 3 are sequentially arranged in the thickness direction. The conductive carbon layer 3 arranged on the other surface of the substrate 2 in the thickness direction is formed by the same method as that of the conductive carbon layer 3 arranged on one surface of the substrate 2 in the thickness direction.

Between the substrate 2 and the conductive carbon layer 3 , or on the lower side of the substrate 2 , one or more functional layers may be further provided. As a functional layer, a base layer, a gas barrier layer, a conductive layer, an adhesive layer, a surface smoothing layer etc. are mentioned, for example. [Example]

Hereinafter, an Example and a comparative example are shown, and this invention is demonstrated more concretely. Furthermore, the present invention is not limited to any Examples and Comparative Examples. Specific numerical values such as the blending ratio (content ratio), physical property value, and parameters used in the following descriptions can be replaced by the corresponding blending ratio (content ratio), physical property value, etc. described in the above "embodiment" The upper limit value (defined as the value of "below" or "less than") or the lower limit value (defined as the value of "above" or "exceeding") of the parameters and other corresponding records.

<Example 1> A substrate 2 including a silicon wafer with a thickness of 280 μm was prepared.

Next, the substrate 2 is set in a sputtering device. The sputtering apparatus is independently equipped with a 1st target, a 2nd target, and a film formation plate. By performing sputtering using this sputtering apparatus, a conductive carbon layer 3 having a target thickness of 40 nm was formed on one surface in the thickness direction of the substrate 2 . Thereby, the electrode 1 provided with the base material 2 and the conductive carbon layer 3 in which the gold nanoparticles 5 were dispersed was obtained. The sputtering conditions are as follows.

1st target: sintered carbon Target 2: Gold Sputtering Gas: Argon Pressure: 0.6Pa Voltage applied to the film-forming plate (ion acceleration voltage): 75 V Power applied to the first target: 400 W Power applied to the second target: 50 W

<Example 2 to Example 4, Comparative Example 1 to Comparative Example 4> Electrode 1 was produced in the same manner as in Example 1. However, as described in Table 1, the voltage applied to the deposition plate, the electric power applied to the first target, and the electric power applied to the second target were changed.

＜Evaluation＞ Regarding the electrodes 1 of Examples 1 to 4 and Comparative Examples 1 to 4, the following items were evaluated.

(1) The content ratio of gold nanoparticles in the conductive carbon layer 3, and sp ³ /(sp ³ +sp ² ) The content ratio of the gold nanoparticles 5 in the conductive carbon layer 3, and sp ³ /(sp ³ +sp ² ) was observed using X-ray photoelectron spectroscopy (XPS, Shimadzu Corporation).

(2) Signal-to-noise ratio when measuring low-concentration arsenic ions (trivalent) Attach an insulating tape with a hole with a diameter of 2 mm to one side of the conductive carbon layer 3 to prepare a sample electrode with a known electrode area. This sample electrode was used as a working electrode, inserted into a 0.05 M H ₂ SO ₄ aqueous solution, and connected to a potentiostat (manufactured by CHI Instruments, ALS730C). Also, similarly, the reference electrode (Ag/AgCl) and the counter electrode (Pt) were inserted into the H ₂ SO ₄ solution and connected to the potentiostat.

Next, H ₂ SO ₄ aqueous solutions were prepared so that the concentrations of arsenic ions (trivalent) in the H ₂ SO ₄ aqueous solution became 0 ppb and 100 ppb, respectively. The reduction deposition potential was set at -0.8 V, and the deposition time was 120 seconds so that arsenic ions (trivalent) were reduced and deposited on the electrode 1 . Thereafter, set the frequency at 50 Hz, the potential increase at 3 mV, and the amplitude at 25 mV, and perform wave voltammetry (SWV) measurements according to different concentrations to obtain SWV curves. In the obtained SWV curve, the peak response current value from the arsenic ion (trivalent) observed at around 0.2 V when the concentration of the arsenic ion (trivalent) is 100 ppb, and the difference between the concentration of the arsenic ion (trivalent) and the solution concentration of 0 ppb In this case, the signal-to-noise ratio (S/N ratio, Signal/Noise ratio) is obtained from the ratio of the current value (corresponding to the value of noise) at the same potential as the peak value.

[Table 1] Table 1 Examples and comparative examples Sputtering conditions Physical properties of conductive carbon layer Electrode activity evaluation Ion acceleration voltage applied to the film forming plate Electricity applied to sintered carbon target Electricity applied to gold target Content ratio of gold nanoparticles sp ³ /(sp ³ +sp ² ) SNR V W W atom% Example 1 75 400 50 3 0.40 183 Example 2 75 400 100 9 0.40 111 Example 3 100 100 5 9 0.25 99 Example 4 25 400 13 4 0.25 206 Comparative example 1 75 400 200 30 0.25 51 Comparative example 2 20 400 5 3 0.20 43 Comparative example 3 20 400 50 15 0.20 61 Comparative example 4 100 100 100 32 0.40 106

In addition, although the said invention was provided as embodiment of the illustration of this invention, it is a mere illustration and should not interpret it restrictively. Variations of the present invention known to those in the technical field are also included in the scope of the patent application described below. [Industrial availability]

The electrodes are used, for example, for electrochemical measurements.

1: electrode 2: Substrate 3: Conductive carbon layer 4: Carbon matrix 5: Gold nanoparticles

Fig. 1 is a cross-sectional view of an electrode according to an embodiment of the present invention.

1: electrode

2: Substrate

3: Conductive carbon layer

4: Carbon matrix

5: Gold nanoparticles

Claims (2)

An electrode, which is provided with a base material and a conductive carbon layer in sequence toward one side in the thickness direction, the conductive carbon layer contains gold nanoparticles dispersed in the conductive carbon layer of less than 10 atomic %, and the conductive carbon layer contains gold nanoparticles dispersed in the conductive carbon layer. The carbon layer contains sp ³ bonded atoms and sp ² bonded atoms, the ratio of sp ³ bonded atoms to the total of sp ³ bonded atoms and sp ² bonded atoms (sp ³ /(sp ³ +sp ² )) 0.25 or more. The electrode according to claim 1, wherein the content ratio of the gold nanoparticles in the conductive carbon layer is less than 5 atomic %.

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